The United States 9-1-1 wireline infrastructure is designed to automatically route Public Switched Telephone Network (PSTN) based 9-1-1 calls to designated geographic Public Safety Answering Points (PSAPs) based upon the ten digit Automatic Number Identification (ANI) of the 9-1-1 caller. The PSAP then confirms the address of the 9-1-1 caller by using the ANI to query subscriber area location information maintained in a local exchange carrier (LEC)-owned distributed database network. This database is updated by the LEC based upon service address information provided by subscribers. Emergency services dispatch can then be made (in instances when the caller cannot assist and/or verbally relay location information) to the registered address of the caller.
Updates have been made to the 9-1-1 wireline infrastructure to handle wireless 9-1-1 calls. Wireless calls are routed to the correct PSAP based on cell identification (ID) information and/or pseudo ten digit ANIs that are generated by third party providers. The PSAP determines caller location by either referencing cell ID-based information or the address associated with the latitude/longitude of the caller provided by the cellular carrier. In both cases area location identification information can be referenced by the PSAP (if the caller cannot assist in providing location information) to assist dispatch, but this may often be inaccurate due to the nomadic nature of cellular service.
Internet telephony, such as Voice over IP (VoIP) phone service, is reportedly poised to become the predominant technology used in the telecommunications industry. Thus, emergency calls will increasingly be placed from VoIP devices. Neither the wireline 9-1-1 infrastructure nor the updated wireless 9-1-1 infrastructure can automatically route VoIP calls to the geographically closest PSAP on a reliable basis. Moreover, even in the case where correct PSAP routing can be made, the 9-1-1 caller's area location identification information will very often be incorrect and cannot be used to assist dispatch in those situations where the caller cannot verbally relay information.